Apparatus for the precipitation of copper from a liquid electrolyte conducted through a multi-cell electrolytic tank

ABSTRACT

In electrolysis installations which possess in a common tank a plurality of anode and cathode plates electrically connected one behind the other, uniform supply to or flow through the individual cells is of greatest importance. According to the invention, the inflow, but also if possible the outflow, is placed below the liquid level, and a distributor pocket for uniform distribution of the liquid is connected between the inflow or outflow of the liquid and its entrance or exit from the electrolytic tank, respectively. For optimum adjustment of the chemical and physical constitution of the liquid, flow-independent measuring and adjusting of the liquid is achieved by a sensor which is arranged in a by-pass to the cycle line of the etching fluid between the etching tank and the electrolytic cell.

FIELD OF THE INVENTION

The invention relates to an apparatus for the precipitation of e.g.copper from a liquid electrolyte by passage of the liquid stream meteredthrough an inlet into the multi-cell electrolytic tank from which itexits through an outlet after precipitation of the copper.

BACKGROUND OF THE INVENTION

In the older processes and apparatus, the liquid electrolyte wasconducted through the multi-cell electrolytic tank in such a way thatuniform precipitation on the electrodes did not occur. This irregularprecipitation results if the liquid distribution in the tank is notabsolutely uniform.

In electrolysis installations possessing a plurality of anode andcathode plates connected electrically one behind the other in a commontank, uniform supply to and flow through, the individual cells is ofgreatest importance. Due to the uniform precipitation of e.g. copperfrom the liquid electrolyte on the electrodes, the precipitated coppercan then immediately be used again in the etching process. Therefore, arecycling process is achieved, among other things.

In one of these known devices the sensor was located in the etchingfluid, which is circulated continuously. Even if one places the sensorinto stagnating areas of the etching tank, the measured result is stillso imprecise that the purpose of the invention, namely to obtain anoptimum etching rate, is not achieved. By immersion of circuit boardsinto the etching fluid, its physical and chemical composition changes.It has been found that to get an optimum etching rate, certainparameters of the chemical and/or physical constitution of the etchingfluid must exist.

The present process relates to ecophile etching, i.e. the etching fluidis circulated continuously. It is not exchanged, as in known processes,when it is used up, but is regenerated or is given additions whichensure that an optimum etching rate exists.

SUMMARY OF THE INVENTION

The object of the invention is, therefore, to conduct the process and todesign the apparatus so that an absolutely uniform distribution of theliquid electrolyte over the electrodes takes place, the liquidelectrolyte to be optimally adjusted with respect to its chemicalproperties.

The solution of the problem of the invention now consists inthat--proceeding from the known processes for the precipitation of e.g.copper from a liquid electrolyte by conduction of the liquid stream,metered through an inlet into the multi-cell electrolytic tank, whenceit issues from an outlet after precipitation of the copper--the liquidstream passes through a liquid receiver formed by the liquid streambefore the inlet located under the liquid level of the electrolytictank, e.g. by the use of a liquid-buffer tank, in order to flow throughthe individual cells of the electrolytic tank with uniform distribution.

Here an entirely new route is taken. Heretofore the liquid electrolytewas indeed allowed to flow into the electrolytic tank metered and asuniformly as possible in a free jet, and via a drain or overflow theliquid stream, from which e.g. copper had now been removed, left thetank again. It turned out that on the electrodes a very unevenprecipitation occurred, outright patterns formed, or where the flow wasespecially strong, no precipitation at all took place.

With the new process the liquid electrolyte no longer flows freely intothe tank. It gets into the tank only via a liquid receiver. By thisliquid receiver it is achieved--and tests have confirmed this--that avery uniform admission of the electrodes by the liquid electrolyteoccurs. Since the velocity of the liquid stream from the inlet towardthe outlet is very low, precisely at these low flow velocities it isimportant to carry out the admission of liquid stream very uniformly onthe inlet side and analogously also on the outlet side to discharge theliquid stream again uniformly, in order that every square millimeter ofthe plates or boards--and there are usually a large number in such atank--is evenly admitted by the liquid stream or respectively a veryuniform precipitation then occurs.

The solution of the problem, namely to achieve an accurate, i.e.flow-independent measurement and adjustment of the etching fluid by asensor, is effected in that the sensor is arranged in a by-pass to thecycle line of the etching fluid between etching tank and electrolyticcell, which is connected at adjustable intervals of time with the cycleline, e.g. via a valve, and the switching phase of the sensor takesplace with the valve closed, i.e. in the by-pass during repose of theetching fluid.

Here an entirely new method is employed. Measuring is no longer donecontinuously, as is customary in such processes, but intermittently. Theintervals of time result by taking from the liquid a sample,transferring it into a measuring vessel and then being able to measurethis liquid accurately in the static state, independent of flow. As afunction of this measured result the etching fluid is then regeneratedor modified by additions until an optimum etching speed exists.

In a preferred embodiment, according to the invention consists in thatthe sensor is a float known in itself, with inductive or capacitive tap.

Further the sensor is appropriately contained in an overflow vesseldisposed in the by-pass line.

This overflow vessel assures that the quantity of sample liquid remainsalways exactly constant.

Appropriately the valve is arranged in the airflow to the overflowvessel.

To ensure automatic operation, it is important that the valve is anelectromagnetic valve whose open and closed position isprogram-controlled.

In a preferred embodiment, it is important that the valve is anelectromagnetic valve whose open and closed position isprogram-controlled.

In a preferred embodiment, in which the copper content in the etchingfluid is adjusted to a certain amount, it is important that the sensorswitches the current supply of the electrolytic cell, e.g. via anamplifier.

The electrolytic cell is used for copper precipitation, and depending onan adjusted value, one is then in a position to assign to the etchingfluid a certain specific gravity according to a specific copper content.

Another possibility is that the sensor regulates the liquid supply tothe electrolytic cell, e.g. via a valve and an amplifier.

If not only the copper content is to be adjusted by a switchableelectrolytic cell, but if other parameters are selected which are to beadjusted to achieve an optimum etching rate, there results a process foretching circuit boards by continuously monitoring the etching fluid inits tank; the teaching of the invention then consists in that theetching fluid is intermittently replenished by additions-depending onthe number of etching operations--until an optimum etching rate isobtained. The process can be carried out exactly only by the fact that asensor monitors the state of the etching fluid in a control vessel whichis filled at selectable intervals of time, and that the measuring phaseof the sensor is shifted to the static phase of the measured liquid inthe control vessel.

A preferred device which solves the problem of obtaining a uniformdistribution of the liquid electrolyte consists in that theliquid-buffer tank is formed by a partition, e.g. one arranged parallelto the inlet side of the electrolytic tank, whose upper edge lies belowthe liquid level of the electrolytic tank, while the lower edge and thelateral edges of this partition are connected water tight with theelectrolytic tank in the manner of a dividing wall.

According to the new process, the construction costs will be very low ifdividing walls are provided in the electrolytic tank on the inlet sideand appropriately also on the outlet side.

This device is adaptable also according to whether the tank is to becharged with the liquid electrolyte from above or from below.

One possibility consists in that the inflow into the liquid-buffer tankoccurs from below under hydrostatic pressure.

By using a buffer tank, therefore, it is here achieved that underhydraulic pressure, as it were, a uniform distribution takes place.

If the tank is to be charged from above, it is essential that the inflowinto the liquid-buffer tank occurs via an additional preceding buffertank, which is charged from above.

The design of the buffer tank or of the dividing walls may be different.One possibility is that the upper edge of the partition extends beyondthe liquid level of the electrolytic tank and the inlet openings in thepartition are arranged below the liquid level.

Depending on the size of the electrolytic tank and the type of liquidelectrolyte, it is possible also that the inlet openings, arrangedapproximately at midheight of the liquid level, conduct the liquidstream evenly between the electrodes.

Also it is possible that instead of a plurality of inlet openings theyare combined in one slit. A further possibility is that there areseveral partitions forming a siphon type receiver.

By using several dividing walls, the liquid stream will always bedistributed evenly in a differentiated manner in an electrolytic tank ofany size with any number of electrodes.

What is important is that the outlet side also has one or morepartitions and the discharge below the liquid level through individualopenings and/or slits occurs in a similar manner as at the inlet.

According to this embodiment, a variety of designs on the inlet side canbe combined with the outlet side. For example, on the inlet side onemight use two dividing walls and on the outlet side only one dividingwall, or one uses on the inlet and outlet sides the same distributiondevices for the liquid stream. Depending on the requirements, the inletopenings in the partitions or dividing walls on the inlet side may bearranged at the top, but still below the liquid level, while on theoutlet side they are located farther down. It is essential that theliquid goes in and out of the electrolytic tank, through openings,slits, overflow edges and the like, which are located below the liquidlevel.

An embodiment of the invention is represented in the drawings.Additional features of the invention will be evident from the drawingsand the description therefor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of the flow pattern in an electrolytictank.

FIG. 2 is a side view illustrating the electrolytic tank with thepartition.

FIG. 3 is a partial perspective view of a second embodiment of thepartition.

FIG. 4 is a partial perspective view of a third embodiment of thepartition.

FIG. 5 is a side view illustrating an etching tank with an electrolyticcell and measuring device.

FIG. 6 is an enlarged side view illustrating the measuring deviceconnected to an etching tank.

DETAILED DESCRIPTION OF THE INVENTION

In FIG. 1, the arrow direction 1 shows the liquid stream of the liquidelectrolyte through the electrolytic tank 3. The liquid stream enters onthe inlet side 6 and leaves the tank on the outlet side 18. Electrodes16 are connected one behind the other as anodes and cathodes. In thisconnection the uniform supply to and flow through the individual cellsis of greatest importance.

According to the invention, in FIG. 2 as illustrated the liquid streamis charged in arrow direction 1 from above through a feed 14. In thiscase a preceding buffer tank 13 must be present, through which theliquid stream flows in arrow direction 24. It then enters theliquid-buffer tank 5, sweeping the additional partition 17, from below.The liquid-buffer tank is formed by a partition 7, whose lateral edges10, 11, and the lower edge 9 are connected with tank 3 and madewaterproof, so as to form a dividing wall. In this partition 7, inletopenings 4 are arranged. These inlet openings may be arranged either atthe top, in the center, or distributed in any manner. If desired, testswill be made to determine how the most uniform admission of theindividual plates is achieved during the precipitation. The onlyessential point is that the inlet openings are always located below theliquid level. Then the electrolyte is conducted in arrow direction 25through the individual cells in such a way that the individualelectrodes 16 experience a uniform distribution of the liquid stream. InFIG. 2 the upper edge 15 of partition 7 is above the liquid level 2, inorder that the inlet openings or slits 4 will be below the liquid level2. It is possible also that the upper edge 8 of partition 7 lies belowthe liquid level 2 and the partition then does not have inlet openings.The supplied liquid stream will then flow below the liquid level 2 inarrow direction 26 over this edge 8.

As indicated schematically in FIG. 2, instead of the upper inflow or,upper feed 14, a lower inflow 12 may be provided. In that case thepreceding buffer tank 13 would be omitted.

In FIG. 4 is it illustrated once more perspectively how inlet openings 4under the liquid level 2 may be arranged in the upper region inside thepartition 7.

In FIG. 2 is indicated schematically also that the outlet side 18 may bedesigned accordingly, it being possible to combine individual elementsof the inlet side with other elements of the outlet side, but inthemselves these elements are identical. In the embodiment, to achieveregulation of the liquid level 2, drains 21 are arranged in a partition20. These drains may again be circular, slit type, or adapted to theflow in some other way. In the embodiment, the liquid flow arriving inarrow direction 25 then passes in arrow direction 27 into the buffertank 28 on the outlet side, which may be designed analogously to thebuffer tank 5 on the inlet side. An additional partition 19, which isarranged at the distance 29 from the bottom of tank 3, then permits thedraining liquid to enter the after-connected tank 23 in arrow direction30. There an overflow 22 is provided, that is to say, the now outflowingliquid gets to the outside in free fall. By this overflow it isautomatically provided that the liquid level 2 remains constant.Although the embodiment described in the following is applicable also toan arrangement according to FIGS. 1 to 4, for better comprehension theorganization of the measuring device is described in a modifiedembodiment.

In FIG. 5, according to a further embodiment, circuit boards 31 areillustrated schematically, which are immersed in arrow direction 43 intothe etching tank 32 in a manner known in itself for the production ofelectric circuits. The etching tank 32 is coupled with an electrolyticcell 33. A sensor 34, in the form of a float 35, is arranged in theby-pass 36 of a cycle line 37. A valve 38, which regulates the inflow toan overflow vessel 40, in which the float 35 is located, can be actuatedby a program control 42. In the embodiment the float has an inductivetap 39 known in the art. The measuring arrangement switches on or offvia its contact terminals 44 when the contact 39 attached to float 35,e.g. a reed contact, gets out of the magnetic field of the exciter coils45 in the stationary part.

The etching fluid 46 is drawn by pump 48 in arrow direction 47 and thusgets into the cycle line 37. In the embodiment of FIG. 5 the cycle linecontains further a water jet pump 49, which draws partial quantities ofregenerated etching fluid out of the electrolytic cell 33 in arrowdirection 50. The pump then conveys the partially regenerated etchingfluid further in arrow direction 51 back into the etching tank 32. Thefeed to the electrolytic cell 33 occurs via a branch 52 when valve 53 isopen. Valve 38 is opened at intervals of time, e.g. by a program control42. Thereby a sample quantity is taken from the etching fluid present inthe cycle line 47 and is passed in arrow direction 54 (cf. FIG. 6) intoan overflow vessel 40. The overflow 55 in this vessel ensures that thequantity to be measured in the measuring tank 56 remains the same. Ifthis measuring tank 56 is full, the excess sample quantity runs in arrowdirection 57 back into the etching tank 32.

Depending on the measurement result, float 35 now moves in arrowdirection 58, so that the contacts 54 e.g. turn off the current supply,not shown, of the electrolytic cell when the copper content in theetching fluid becomes too high, or turn it on again when it becomes toolow.

Additional valves 59, 60 may be switched, which via lines 61, 62 feedadditions into the etching tank 32. Depending on the type of etchingfluid and/or the materials of the circuit boards, this additions bringthe etching rate to an optimum.

I claim:
 1. An apparatus to precipitate a metal element from a liquid electrolyte comprising:(a) an electrolytic tank having an inlet side with an inlet opening, and an outlet side with an outlet opening submerged in said liquid electrolyte; (b) at least one inlet partition positioned parallel to said inlet side of said electrolyte tank and having a lower edge and two lateral edges forming a waterproof wall with inside lateral walls of said electrolytic tank to define a liquid buffer container with said inlet side of said electrolytic tank, and a thruway of said partition submerged in said liquid electrolyte, said partition controlling a speed of said liquid electrolyte as it travels in a path from said inlet side to said outlet side of said tank; (c) at least one anode and one cathode; and (d) at least one outlet partition of a number equal to a number of said inlet partitions and positioned parallel to said outlet side of said electrolytic tank defining an outlet buffer container and controlling an outflow of said liquid electrolyte from said electrolytic tank, said outlet partition having an outlet thruway submerged in said liquid electrolyte.
 2. An apparatus according to claim 1, wherein said inlet and outlet thruways of said inlet and outlet partitions are openings disposed in said inlet and outlet partitions facilitating the uniform flow of the liquid electrolyte through the electrolytic tank.
 3. An apparatus according to claim 2, wherein said inlet thruways comprise a top edge of said inlet partitions.
 4. An apparatus according to claim 2, wherein a second inlet partition is arranged parallel to said first inlet partition between said first inlet partition and said inlet side of said electrolytic tank to define a preconnected buffer container receiving a charged stream of said liquid electrolyte from an admission unit, and an entrance channel is formed between a bottom edge of said second partition and an inside bottom side of said electrolytic tank facilitating a movement of said charged stream from said preconnected buffer container to said liquid buffer container.
 5. An apparatus according to claim 4, wherein a second outlet partition is arranged parallel to said first outlet partition between said first outlet partition and said outlet side of said electrolytic tank to define a buffer container between said first outlet partition and said second outlet partition, and an after-connected container between said second partition and said outlet side of said electrolytic tank, said second partition forming a channel between a bottom edge of said second partition and the bottom side of the electrolytic tank facilitating the uniform movement of the liquid electrolyte from said outlet buffer container to said after-connected buffer container.
 6. An apparatus according to claim 1, wherein said outlet side of said electrolytic tank comprises an overflow drain insuring a constant level of said liquid electrolyte in said electrolytic tank.
 7. An apparatus according to claim 1, wherein said apparatus further comprises means for detecting a specific level of the metal element in the liquid electrolyte.
 8. An apparatus according to claim 7, wherein said means for detecting said specific level of said metal element comprises a cycle line connecting said electrolytic tank to an etching tank in a manner permitting the liquid electrolyte to flow between said tanks, a sensor positioned on said cycle line between said electrolytic and etching tank and measuring a specific amount of the liquid electrolyte, a valve positioned at a bypass on said cycle line and regulating an amount of the liquid electrolyte flowing through said cycle line to said sensor, and a pump conveying the liquid electrolyte through said cycle line.
 9. An apparatus according to claim 8, wherein said sensor comprises a float located in an overflow vessel on said cycle line, said float having a set of inductive contact tabs encompassed in a pair of contact terminals positioned at a bottom end of said float.
 10. An apparatus according to claim 8, wherein said valve is electromagnetic and is regulated between an open and closed position at regular time intervals by a controlled program as said float moves through a magnetic field of said contact terminals. 